In today's computing environment, customers want an easy way to expand their computer systems to include more resources, such as central processing units (CPUs), memory, and/or input/output (I/O) devices, etc. Components called cells provide customers with that capability. For example, cells are components that include any permutation of CPUs, memory, and/or I/O devices, among other things. A computer system can be expanded by installing cells into the computer system. Frequently, the cells can be installed without re-booting the computer system simply by plugging the cell into the computer system (commonly referred to as “hot plugging” or “plug-and-play”), for example. Frequently, a “root cell” can be installed on a computer system. Besides CPUs, memory, and/or I/O devices, a “root cell” can include additional special resources, such as console devices and/or fixed registers. The operating system (OS) can use the fixed registers for system events, for example.
Advanced Configuration and Power Interface (ACPI) is a computer language that can be used for writing parts of a computer system's firmware. ACPI can be used for providing information about cells (e.g., describe cells) to a computer system, among other things as will become more evident. In conventional systems, the root cell of a computer can not be hot plugged for computer systems that use ACPI to describe cells because ACPI defines registers associated with the root cell as “fixed registers,” using a “fixed address descriptor table” (FADT). The “fixed registers” are specified in the FADT and when the computer system is booted up, the operating system proceeds to use the registers specified in the FADT for various system events, for example. The operating system is informed of which registers to use as fixed registers and there is no way to use different registers without modifying the FADT and re-booting the computer system. Therefore, there is no way to “hot plug” a different cell with a different set of fixed registers into the computer system as the root cell.
For these and other reasons, there is a need for a method and/or an apparatus that provides for switching the root cell for a computer system without requiring the computer system to be re-booted.